Dense Iron Cuirass

 is an item  in Tales from the Tiers.

Description
While only the Forge-Bound possess the secrets of making safe and efficient use of iron, others have worked the heavy material over the centuries. This particular sample boasts thick, roughly-hewn iron plates stamped with the seal of the royal house of Azure. Unfortunately, rust has begun to claim the edges of the armor, obscuring the maker's mark.

Location
Stone Sea random encounter (you must search the collapsed building down the slope).